When attaching an electrical terminal to an electrical component such as a capacitor, some structure and method must be employed to form a good mechanical bond between the terminal and the component, and also simultaneously a good electrical connection from the terminal to the electrical elements within the component itself, such as the plates of a capacitor.
If the electrical component and its interior electrical elements can withstand high heat, then direct or semi-direct connections can be made from the terminal to the electrical component, using methods such as welding or soldering. But most capacitors and many other types of electrical components (e.g. thin film resistors) strive for compactness, and so employ interior electrical elements that are thin and fragile, incapable of withstanding high heat. In this case, an intermediary structure is often employed, to make a connection between the electrical component and its terminal.
One such type of intermediary structure is a metal spray. Molten metal is sprayed onto the electrical component at suitable locations, and is allowed to solidify, and the terminal is later attached to this layer of metal that has been sprayed.
A problem has been the composition of this intermediary metal spray structure. There are two primary desiderata for this composition.
First, the material constituting the metal spray should have a low melting point, so that it can be sprayed in molten form onto the electrical component at a relatively low temperature, thereby minimizing the amount of potentially damaging heat inflicted upon the electrical component. A metal spray with a low melting point is further advantageous for later welding or soldering of the terminal to the end spray.
Second, the material constituting the metal spray should also have high conductivity, so as to form a good electrical connection between the terminal and the component.
Unfortunately, these two desiderata tend to be mutually exclusive. Metal materials having a suitably low melting point tend to have the poorest conductivity among metals, while metal materials with the best conductivity tend to have melting points too high to be suitable for molten spraying onto fragile electrical components.